Technical Field
The present disclosure relates to an image processing device and an image processing method for processing images of an eye fundus of a subject eye taken along a time course and relates to a program for causing a computer to execute the image processing method.
Description of the Related Art
In a visual function which is assumed to be an important function among five senses of humans, photoreceptor cells of the retina positioned at an eye fundus of a subject eye plays an important role. Recently, techniques of taking images of the retina at the eye fundus with high definition have been established using an aberration correction (compensation) technique, and finding of new knowledge and establishment of diagnostic values about the visual function are expected.
An adaptive optics scanning laser ophthalmoscope (hereinafter, referred to as “AO-SLO”) apparatus is an ophthalmoscope which applies the techniques of telescopes of acquiring clear star images by compensating for fluctuations in air to image-taking of eyes. This AO-SLO apparatus enabled resolving of each one of the photoreceptor cells of the retina of the subject eye. It is said that, in the vicinity of the fovea centralis (fovea) where the photoreceptor cells have a highest density, the photoreceptor cells are present at an interval of about 2 μm. Today, in order to draw up to the photoreceptor cells of the fovea centralis, development for improving the resolution is being continued.
In order to lead to clinical values of the taken images of the photoreceptor cells, the techniques capable of observing the photoreceptor cells in the same region of the eye fundus along a time course and quantitatively analyzing changes thereof are required. In many cases, the images taken by the AO-SLO apparatus (hereinafter, referred to as “AO-SLO images”) have small view angles (image-taking ranges are small) since the resolutions thereof are high. Therefore, in order to perform time-course comparison of images, first, a plurality of AO-SLO images taking the same region have to be acquired, and, furthermore, fine registration has to be performed between the acquired images. As a conventional technique about this, for example, there is a technique of Japanese Patent Laid-Open No. 2007-252692.
Specifically, Japanese Patent Laid-Open No. 2007-252692 discloses the techniques in which, in order to perform time-course comparison between tomographic images of the retina by OCT (Optical Coherence Tomography), surface images (eye-fundus images) of the eye fundus are acquired at the same time as the tomographic images; then, first, the surface images are registered with each other; and, then, the tomographic images associated with the surface images are registered with each other to perform comparison.
However, in the techniques disclosed in Japanese Patent Laid-Open No. 2007-252692, since the surface images to be registered have to be specified first, the comparison of the small-view-angle surface images of the eye fundus of the subject eye cannot be efficiently performed.
Accordingly, there is a need to provide a mechanism capable of efficiently performing the comparison of small-view-angle surface images of the eye fundus of the subject eye.